Under each sub category there will be similar category names.
Ie under apple there will be juice, and cups.
Under orange there will be juice, and cups.
The contents of each will of course be different depending upon the sub category.

If I used the www.example.com/apple/juice/product it would be nice because it is less clicks, but a negative because instead of one easy category on menu bar with more nested, I now have many.

My concern is the aspect of parent/nested categories and hurting SEO, by url length and the final product being 4 clicks away.

Well url length should be no longer than 75 to 115 characters long.

There is no correlation between url length and click depth. Click depth is how many clicks to get to the page from the home page,not how many sub directories ther are, and if the item is in the main navigation structure then the page is only "1", I repeat, "ONE", click away from the home page.
Go examine this >>>>> https://superfish.joelbirch.co/examples/supersubs/
It shows a menu with sub menus that have sub menus, this will fix your click depth problem. Not saying it is a copy and paste solution.

If sub menus with sub menus is not an option, then the click depth for www.example.com/apple/ would be 1 click
then /juice/ would be 1 click if you have multiple sub categories in apple and any product would be just 1 click, so I only see 2 to 3 clicks in depth. Anything over 4 clicks I would consider putting it in the footer of your site. An ideal place for deep pages on your site, makes a 5 click deep page a single click by putting it in the footer. An accepted SEO practice. Recommended by Google and others also.

I happen to like www.example.com/apple/juice/product/ verses www.example.com/shopbyfruit/apple/juice/product/
The first looks cleaner and more readable and to the point, also shorter.